Preparation of amides



Jably above the temperature used in the process.

Un d at Paten PREPARATION OF AMIDES Giuliana C. Tesoro, 'Dobbs Ferry, N. Y.-, assignor to Onyx Oil & Chemical Company, Jersey City, N. 1., a corporation of Delaware No Drawing. Application June '29, 1955 Serial No. 518,959

14 Claims. (Cl. 260-404) This invention relates to an improved method of aminolysis of esters, and particularly of higher fatty acid esters, with high boiling amines, and more particularly it relates to the manufacture of diethanolamides of higher fatty acids. 1 v

The process of the present invention is an improved method of aminolysis of esters, and particularly of higher fatty acid esters, with high boiling amines, and particularly with diethanolamine, at a low temperature and under reduced pressure in the presence of an alkaline catalyst, and particularly of sodium methoxide as a catalyst. I

The invention relates more particularly to a process of aminolysis of esters with high boiling amines, in which the high boiling amines, together with the catalyst, are heated to a temperature of about 55-75 C., advantageously to about 5565 C., and the cold higher fatty acid ester is added gradually or progressively, whereby the exothermic heat of reaction is largely oifset by the cooling effect of the added ester; and the reaction mixture is advantageously maintained under a vacuum to avoid contact of the reaction mixture with the air andto remove volatile constituents formed during the reaction.

The improved process is of particular value in the production of higher fatty acid amides from high boiling amines, and particularly from diethanolamine, by adding methyl esters of the higher fatty acids to the high boiling amines and catalyst at a temperature of around 55 -75 C., and advantageously of about 55 65 C., and under a vacuum which removes the methyl alcohol as it is formed during the process. The carrying out of the process in this way avoids objectionable foaming by the methyl alcohol formed and removed and the distillation of the methyl alcohol during the process under a vacuum aids in neutralizing the exothermic heat of reaction.

The process is also an advantageous process for the production of amides of higher fatty acids by the gradual or progressive addition of triglycerides to the hot amine with admixed catalyst.

It is one advantage of the present process that it enables a high yield of amide to be produced with minimizing of the production of undesirable byproducts and with advantages in the heat control of the process by oifsetting of the exothermic heat of reaction by the cooling effect of the gradually or progressively added cold ester, and by distillation of volatile reaction products, e. g., of methyl alcohol where methyl esters are used.

The esters which are used in carrying out the present ,process are esters of higher fatty acids including triglycerides such as cocoanut oil and esters of monohydric alcohols and particularly methyl esters of higher fatty acids such as methyl laurate, methyl myristate or methyl esters of cocoanut oil fatty acids, etc.

The amines which are used in carrying out the process are high boiling amines with a boiling point consider- The process is of special advantage for the production of 2,844,609 Patented July 22,. 1 958 Z amides of diethanolamine. Other high boiling amines can be similarly used, such as monoethanolamine, hydroxy ethyl ethylene diamine, etc.

The alkaline catalyst used is advantageously sodium methoxide. The sodium methoxide is advantageously, added as such or may be formed by the reaction of other sodium compounds such as metallic sodium or sodium amide, etc., where the reaction mixture contains methyl alcohol or where methyl esters are used in the process.

The improved process of the present invention is well adapted for use on a large scale with avoidance of difficulties due to exothermic heat of reaction and with production of a high yield of a product of high purity.

In carrying out the process, the amine, e. g., diethanolamine, together with the catalyst, e. g., sodium methoxide, is placed in the reaction vessel and heated to a temperature of around 55-75 C., and advantageously around 55-65 C., and the apparatus is advantageously maintained under a vacuum, e. g., corresponding to 30-40 mm. of mercury. The cold ester, such as the triglyceride or methyl ester of higher fatty acid, is then added gradually or progressively or stepwise, so that the amine is in excess and so that volatile reaction products such as methyl alcohol, Where methyl esters are added, is progressively removed during the process. The apparatus Will normally be provided with heating and cooling means to aid in the temperature control. But the cooling effect of the cold ester as it is-progressively added, and such cooling as results from the distillation of methyl alcohol, when methyl esters are added, are effective in neutralizing the exothermic heat of reaction so that any considerable or objectionable rise in temperature is avoided and so that a minimum of control by the heating or cooling means is required or may be entirely unnecessary.

The improved process of the present invention has many advantages, including the following:

The operation can be carried out on a large scale without difiiculties of heat control due to exothermic heat of reaction; objectionable foaming is avoided when volatile high boiling products are formed such asmethyl alcohol which is progressively removed during the process as the methyl ester is progressively added; and the reaction time is relatively short, e. g., 1-'2 hours, even at the relatively low temperature employed; the yield obtainable approaches the theoretical optimum; the formation of objectionable byproducts, particularly where the secondary amine contains hydroxyl groups such as diethanolamine, is minimized as compared with high temperatures and prolonged heating, which increases the amount of objectionable byproducts such as amino esters and amido esters; due to the mild conditions employed, the physical appearance of the products, e. g., color and odor, is excellent; and due to the virtual absence of byproducts, the performance of the products, e. g., as foam stabilizers, is improved.

In carrying out the'process for producing the amides by reaction of fatty acid estersv suchas methyl laurate or methyl myristate or'cocoanut oil (the triglyceride of cocoanut oil fatty acids) or the methyl esters of cocoanut oil acids, etc., and non-volatile alkylolaminessuch as monoethanolamine or diethanolamine, the following conditions are advantageous: the raw materials are essentially free from moisture to avoid decomposing the catalyst by the water present; the amount ofcatalyst should be in excess of the amount inactivatedby the moisture and by free fatty acid present in'the raw mamoisture which may be present in the equipment or accidentally introduced. The catalyst is preferably used in alcoholic solution and is added to the amine and the amine heated to a temperature which is advantageously around 55 -65 C., e. g., about 60 C. under a vacuum of e. g. to mm. of mercury. The vacuum can be varied but should be sufiicient to prevent air from entering the apparatus and to remove readily volatile constituents and particularly methyl alcohol produced when methyl esters are used. The temperatures can be varied somewhat from the range of '5565 C. and a somewhat higher temperature, e. g., 7075 C. or somewhat higher, does not materially change the nature of the process or the advantages obtained with it. At the end of the process, the catalyst is neutralized, advantageously while a vacuum is still maintained on the apparatus, by adding the calculated amount of a weak acid such as acetic or glycolic (hydroxyacetic) acid, in order to lower the pH and also in order to prevent rearrangement and deterioration on storage. When acetic acid is added, sodium acetate is formed, which dissolves in the product. When glycolic acid is used, sodium glycolate is formed and precipitates out and is readily removed by filtration at about C. i

' It is one advantage of the process that molecularly equivalent proportions of the ester and amine can be used with the production of a high yield of amide.

An excess of amine, over the equivalent proportions, can readily be used when a product is desired which contains an excess of amine. And when an excess of amine is used, the process has the advantage of avoiding or minimizing the formation of byproducts such as result on heating to higher temperatures such as have heretofore been used in the production of amides with the use of an excess of amine.

In carrying out the process, after the amine and catalyst have been heated to the proper temperature, the proper or calculated amountof ester is added, either gradually or progressively or in portions or stepwise, and the rate of addition is regulated by the reaction temperature and to maintain a proper temperature. The rate of addition is also such that when volatile alcohols such as methyl alcohol are formed, they will be progressively removed without objectionable foaming and without accumulation of any large amounts of alcohol in the reaction mixture.

The addition of the cold ester, and the controlled evaporation of a volatile alcohol under the vacuum where such an alcohol is formed, makes external cooling unnecessary to neutralize the heat of reaction, or mini- 'mizes the amount of external cooling required. And if the cooling elfect of the added ester and of the evaporation of the alcohol is not sufficient to efiect complete neutralization of the heat of reaction, a limited increase in temperature, e. g., to a temperature somewhat in excess of 65 C., is unobjectionable, since this increase is limited in amount.

The time required for carrying out the process will vary somewhat but, in general, with a maintenance of the temperature within the range of around -65 C. throughout the addition of the ester, the process requires about an hour, more or less.

The process will be'further illustrated by the-following specific examples, but it will be understood'that the invention is not limited thereto. The parts are'by weight. The apparatus used in thefollowing examples was an apparatus which was glass-lined or which had glass in contact with the reacting materials. Stainless steel apparatus can'be similarly used.

Example 1.94.5 parts of diethanolamine and 3.2 parts of sodium methylate are charged in a vessel equipped with mechanical stirrer: and with thermometer and charging funnel, and connected to. a vacuum distillation apparatus. The pressure 'onilthefapparatus lis de- *creased to about :40 :mmaofzmercury: .and the;temperature of the mixture of diethanol-arnine and catalyst is raised to about 60 C. 128.4 parts of methyl laurate (of purity, i. e., containing a minimum of 90% by weight of methyl laurate, the rest being mostly methyl esters of higher and lower boiling fatty acids of the cocoanut oil) are then introduced in portions of about 12 parts every 10 minutes over a period of about 2 hours while maintaining the vacuum and the temperature at 55-65 C. With this rate of addition under a vacuum, the accumulation of methanol in the reaction mixture is avoided and methyl alcohol is distilled from the mixture without objectionable foaming. 20 minutes after the completion of the adding of the ester, the mixture is free of methanol. In this case, an excess of amine is used over that equivalent to the methyl esters added and substantially complete conversion of the methyl esters into bis(hydroxyethyl) lauramide is efiected, giving an amide product of high purity admixed with the excess of diethanolamine.

This method is advantageous where a product is desired which contains an excess of amine in addition to the amide.

The following examples illustrate the use of substantially equivalent proportions of amine and ester.

Example 2.-229 parts of diethanolamine and 47 parts of a 25% solution of sodium methylate in methanol are charged in a glass lined jacketed kettle equipped with agitator and temperature recorder and connected to a vacuum pump. The kettle is evacuated to a vacuum of about 29 inches of mercury and the temperature of the mixture of diethanolamine and catalyst is raised to 65 C.

458 parts of methyl laurate are then added under a vacuum at the rate of 50-80 parts every 10 minutes, with maintenance of the temperature at 5565 C. '30 minutes after completion of the addition of the ester, all the methanol has been removed from the reaction mixture and titration of the free diethanolamine indicates 92% conversion to lauric diethanolamide. 25 parts of hydroxyacetic acid are then added to neutralize the catalyst, and the sodium hydroxy acetate which is formed and precipitated is removed by filtration at about 50 C. 0n standing, the filtrate solidifies to a cream-colored crystalline mass.

Example 3.292 parts of diethanolamine and 71 parts of 25% sodium methylate in methanol are charged in a glass-lined jacketed kettle equipped with temperature recorder, agitator and vacuum line. The kettle is evacuated and the temperature of the charge is raised to 65 C. 680 parts of crude cocoanut oil are then added under vacuum at the rate of 50 parts every 5 minutes and with maintaining of the temperature at 55-65 C. 20 minutes after completion of the addition of the ester, the reaction is essentially complete and titration indicates that about 92% of the diethanolamine has been converted to amide. 21 parts of glacial acetic acid are then added to neutralize the catalyst. The resulting product contains about 3% sodium acetate and 10% of glycerol and is a clear, amber-colored viscous liquid.

The product is an excellent foam stabilizer, e. g., when added in the ratio of 1 part to 3 parts by weight of a technical grade of sodium lauryl sulfate.

Example 4.3 15 parts of diethanolamine and 61 parts of 26% sodium methylate in methanol are charged in a vessel equipped with mechanical stirrer, thermometer and addition funnel, and connected to a vacuum distillation apparatus. The pressure is decreased to about 60 mm. of mercury, and the temperature is raised to 65. 720 parts of methyl myristate (96%) are then added in portions over a period of 1 /2 hours, maintaining the temperature at 6570, and the pressure low enough to allow the methanol formed to distil as fast as it is formed. One hour after completing the addition of the ester, all the methanol has been removed and titration indicates that 93% of the diethanolamine has been converted to the corresponding amide. On cooling, the product solidifies to a. hard, waxy, crystallinesolid.

Example 5.l22 parts of monoethanolamine and 40 parts of a 26% solution of sodium methylate in methanol are charged in a vessel equipped with mechanical stirrer, thermometer and addition funnel and connected to a vacuum distillation apparatus. The mixture is heated to 60, and the pressure decreased to about 50 mm. of mercury. 440 parts of the methyl ester of whole cocoanut fatty acids are then added in portions, over a period of one hour, maintaining the temperature at 6065 and the pressure at 40-60 mm. of mercury. Twenty minutes after completing the addition, the calculated amount of methanol has been distilled off and titration indicates that the monoethanolamine has been quantitatively converted to the corresponding amide. On cooling, the product solidifies to a pale yellow crystalline mass.

Example 6.l04 parts of hydroxyethyl ethylene diamine and 5.3 parts of sodium methylate are charged in a vessel equipped with mechanical stirrer, thermometer and addition funnel and connected to a vacuum distillation apparatus. The temperature of the mixture is raised to 55 and the pressure decreased to 40-50 mm. of mercury. 290 parts of methyl stearate are then added over a period of one hour, maintaining the temperature at 5065 and the pressure at 40-50 mm. One hour after completing addition of the ester, the reaction is essentially complete and the methanol has been completely removed. On cooling, the stearic acid mono amide of hydroxyethyl ethylene diamine solidifies to a waxy crystalline mass.

In some of the above examples, neutralization of the catalyst is not referred to, but ordinarily the catalyst will be neutralized, e. g. with acetic acid or hydroxyacetic acid, as illustrated in Examples 2 and 3.

In a similar manner, other high boiling amines and particularly other high boiling alkanolamines can be similarly reacted with esters for the production of amides.

The process of the present invention enables high yields of amides to be produced from the esters and amines, and amides of high purity.

I claim:

1. The method of producing amides from higher fatty acid esters of the class consisting of the lower alkanol esters and glyceride esters of higher fatty acids and high boiling alkanolamines of the class consisting of primary and secondary alkanolamines which comprises heating a mixture of the high boiling alkanolamine and a sodium methoxide catalyst to a temperature of about 5575 C. and gradually adding the cold fatty acid ester to the amine and catalyst while maintaining a vacuum.

2. The process acconding to claim 1 in which the temperature is maintained at about 5565 C.

3. The method of producing amides from higher fatty acid esters of the class consisting of the lower alkanol esters and glyceride esters of higher fatty acids and high boiling alkanolamines of the class consisting of primary and secondary alkanolamines which comprises heating a mixture of the high boiling alkanolamine and a sodium methoxide catalyst to a temperature of about 55 -75 C. and gradually adding the cold fatty acid ester to the alkanolamine and catalyst while maintaining a vacuum.

4. The method of producing amides from higher fatty acid esters of the class consisting of the lower alkanol esters and glyceride esters of higher fatty acids and diethanolamine which comprises heating a mixture of the diethanolamine and a sodium methoxide catalyst to a temperature of about 55 -75 C. and gradually adding the cold fatty acid ester to the diethanolamine and catalyst while maintaining a vacuum.

5. The process according to claim 4 in which the temperature is maintained at about 5565 C.

6. The method of producing amides from methyl esters of higher fatty acids and high boiling alkanolamines of the class consisting of primary and secondary alkanolamines which comprises heating a mixture of the high boiling alkanolamine and a sodium methoxide catalyst to a temperature of about 55 75 C., and gradually add iug the cold fatty acid methyl ester to the amine and catalyst while maintaining a vacuum suflicient to remove the methyl alcohol formed by the reaction.

7. The process according to claim 6 in which the temperature is maintained at about 55-65 C.

8. The method of producing amides from triglycerides of higher fatty acids and high boiling alkanolamines of the class consisting of primary and secondary alkanolamines which comprises heating a mixture of the high boiling alkanolamine and a sodium methoxide catalyst to a temperature of about 55 -75 C. and gradually adding the cold triglyceride to the amine and catalyst while maintaining a vacuum.

9. The method of producing amides from methyl esters of higher fatty acids and diethanolamine which comprises heating a mixture of the diethanolamine and a sodium methoxide catalyst to a temperature of about 55-75 C. and gradually adding the cold fatty acid methyl ester to the diethanolamine and catalyst while maintaining a vacuum sufficient to distill the methyl alcohol formed by the reaction.

10. The method of producing bis(hydroxyethyl) lauramide from methyl laurate and diethanolamine which comprises heating a mixture of the diethanolamine and a sodium methoxide catalyst to a temperature of about 5575 C. and gradually adding the cold methyl laurate to the diethanolamine and catalyst while maintaining a vacuum sufiicient to distill the methyl alcohol formed by the reaction.

11. The process according to claim 10 in which the temperature is maintained at about 55-65 C.

12. The method of producing amides from triglycerides of higher fatty acids and diethanolamine which comprises heating a mixture of diethanolamine and a sodium methoxide catalyst to a temperature of about 55 75 C. and gradually adding the cold triglyceride to the diethanolamine and catalyst while maintaining a vacuum.

13. The method of producing amides from cocoanut oil and diethanolamine which comprises heating a mixture of the diethanolamine and a sodium methoxide catalyst to a temperature of about 55-75 C. and gradually adding the cold cocoanut oil to the amine and catalyst while maintaining a vacuum.

14. The process according to claim 13 in which the temperature is maintained at about 55-65 C.

References Cited in the file of this patent UNITED STATES PATENTS 2,464,094- Meade Mar. 8, 1949 

1. THE METHOD OF PRODUCING AMIDES FROM HIGHER FATTY ACID ESTERS OF THE CLASS CONSISTING OF THE LOWER ALKANOL ESTERS AND GLYCERIDE ESTERS OF HIGHER FATTY ACIDS AND HIGH BOILING ALKANOLAMINES OF THE CLASS CONSISTING OF PRIMARY AND SECONDARY ALKANOLAMINES WHICH COMPRISES HEATING A MIXTURE OF THE HIGH BOILING ALKANOLAMINE AND A SODIUM METHOXIDE CATALYST TO A TEMPERATURE OF ABOUT 55*-75*C. AND GRADUALLY ADDING THE COLD FATTY ACID ESTER TO THE AMINE AND CATALYST WHILE MAINTAINING A VACUUM. 